Hiya
Deviants are either COLOUR or PATTERN gene enhancements.
Both parents must have double of the same gene in order for the baby to be deviant. E.g.
Mother Father
Chestnut/Chestnut Chestnut/Chestnut
Cream/Cream Cream/Cream
They're both homozygous cremellos. You could get either type of deviant because they're both a perfect match.
For a double deviant, you'd need a perfect match like the one above, but the mother would have to be colour deviant (chesnut*) and the father pattern deviant (cream*) or vice versa.
10% chance of getting a dev from any breeding, but the parents have to be homozygous (sometimes they aren't, and you get a homoz baby that's also a dev, but it very seldom happens).
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